Air filter



J. J. KLEIN AIR FILTER Filed Aug. 6, 1957 June 13, 1961 United States Patent O 2,988,169 AIR FILTER Joseph J. Klein, Glencoe, Ill., assignor to Fiber Bond Corporation, a corporation of Illinois f Filed Aug. 6, 1957, Ser. No. 676,657 8 Claims. (Cl. 183--49) This invention relates to an air lter, and is particularly concerned with a self-sustaining deformable air filter that may be inserted into an opening of any shape and frictionally held therein in sealing engagement with the wall surfaces of the opening.

The air lter of the present invention is particularly adapted for use with air conditioning or heating systems and comprises an adhesively bonded fibrous web bonded to a backing of resin coated open cloth which serves as a reinforcement, and also helps the fibrous web retain its shape when the edge portions of the filter are deformed to fit in an opening in an air conditioning or heating system.

The web comprises a plurality of non-absorbent, nonmatting fibers, preferably plastic fibers, either straight or curled, of various lengths of from about one-half inch to two inches, held in three-dimensional, random arrangement by means of a flexible adhesive. The individual fibers are first arranged in a three-dimensional, random arrangement and are then wetted lightly with adhesive to cause them to adhere to each other only at their spaced points of contact.

The adherence of the three-dimensional, randomly arpoints of contact imparts excellent air retaining and insulating qualities to the web. Air can pass readily.

less of surface irregularities, without losing its air retaining or insulating qualities.

Any adhesive which gives a fiexible bond may be used in accordance with the present invention, but an elastic adhesive such as natural or synthetic rubber deposited from a latex emulsion is preferred. A suitable synthetic rubber is a vulcanizahle, rubbery copolymer of butadiene and acrylonitrile, for example, that sold by B. F. Goodrich Co. under the trademark CarbopoL The web is bonded to a backing of resin coated open cloth such as tobacco cloth, screening cloth, Dixie netting, leno cloth and the like, or other foraminated selfsustaining deformable material of 4 to 16 mesh openings to the inch, preferably 4 to 6. The backing has spaced slits extending inwardly from its outer edge to facilitate bending the edge portions to form a rim extending perpendicularly to the body portion of the filter. If the filter has straight sides, the corners are preferably slit diagonally.

A tape is wrapped around the perpendicular edge portions to impart strength to the filter. Preferably the tape is applied to the web side of the filter. The filter may be deformed to fit frictionally against the inner wall surfaces of the duct or other opening in which it is to be used. The perpendicular rim presses the fibrous web against the wall surfaces. Due to the yieldable, deformable character of the fibrous web, it conforms to the surface irregularities of the duct, thereby providing an effective edge seal against egress of air about the peripheral edges of the filter. The resilience of the fibrous web, to which the tape is adhered, permits the tape to be deformed along with the rim of the filter.

Instead of adhering the tape to the rim of the filter before the filter is positioned within the duct or other opening in which it is to be used, the tape may be adranged fibers to each other at substantially only theirdeformed and positioned. In such case the tape may extend over the free edge of the rim so as to be adhered partly to the rim of the filter and partly to the wall surface of the duct or other opening in which the filter is positioned. i

Preferably the tape is of less width than the height of the rim of the filter, so that the fibrous web will project beyond at least one edge of the tape to form an efficient seal between the edge of the filter and the wall surface of the duct or other opening in which it is positioned.

The web is preferably adhered to the outer surface of the backing material, but in an alternative form of the invention the backing material may be applied to both surfaces of the web.

A preferred illustrative embodiment of an air filter incorporating the above and other advantages is shown in the accompanying drawing, forming part of this specification, in which:

FIG. 1 is a fragmentary perspective view of a duct which may be part of an air conditioning or heating system, with an air filter positioned therein;

FIG. 2 is an enlarged cross sectional view, taken along the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary plan view of the air filter, showing diagonal slits at each corner; and

FIG. 4 is a fragmentary perspective view, showing the filter secured in the duct.

In the drawings, the reference numeral 2 indicates a backing of resin coated open-work textile fabric of selfsustaining deformable foraminated material, such as Dixie netting, leno cloth, tobacco cloth and the like, capable of holding any shape into which it is placed. The fabric may lhave from 4 to 16 mesh openings to the inch, but preferably is within the range of from 4 to 6 openings to the inch.

A web 3 of three-dimensional, randomly arranged fibers is bonded to the open-work textile fabric backing. The fibers preferably are curled or crimped, but straight fibers of the same type may be used. The fibers may be natural fibers, such as hogs hair, or they may be synthetic fibers such as nylon, rayon, acrylic fiber (a copolymer of vinyl chloride and acrylonitrile), commercially available under the trademark Orlon, or polyvinylidene chloride-polyvinyl chloride copolymer fiber, commercially available under the trademark Saran Nonorganic fibers such as glass fiber, commerically available under the trademark Fiberglas, may also be used. Any of these fibers may be used alone or mixed with each other.

The fibers are preferably of various lengths, from about one-half inch to two inches, and are intermingled in random arrangement so that they lay at various angles, both horizontally and vertically, to form a. three-dimensional web with the individual fibers contacting each other at their separate points of contact throughout the web. Relatively few pairs of individual fibers contact at more than one point, and each ber of the web contacts a plurality of other fibers at spaced points which may be in the same or in different planes.

The fibers are laid on the foraminated backing 2 in any suitable manner, and the web and backing are sprayed or otherwise coated lightly with an elastic adhesive on either one or both surfaces, preferably both surfaces.

The amount of adhesive is sufficient to coat atleast the outer fibers of the web so that they adhere to each other and to the foraminated backing at the points of contact only. The small amount of adhesive which passes through the interstices between the outer fibers wets the underlying fibers and causes them to adhere at their points of contact. The amount of adhesive is not suffi,-

cient to fill the voids between the fibers. It is not essential that the adhesive reach fibers in the center of the web. The adhesive serves to tie the whole web together by joining fibers extending transversely of the web with the longitudinally extending fibers at both ends ofthe transversely extending fibers.

Any elastic adhesvie material such as natural rubber, synthetic rubber, or adhesive resinous or other plastic material may be used. The adhesive material may be applied in solution or in emulsion form. In the case of either natural or synthetic rubber, for example, it is applied in the form of an aqueous suspension or latex, with or without vulcanizing agents, and the adhesive coating is then dried to precipitate the rubber. Any conventional, commercially available, ammonium-stabilized, natural rubber latex may be used in accordance with my invention, along or in combination with a synthetic rubber latex.

A suitable synthetic rubber latex which may be used as the adhesive is the rubbery copolymer of butadiene and acrylonitrile sold under the trademark CarbopoL If desired, there may be incorporated into the natural rubber latex or the mixed natural and synthetic rubber latex small amounts, about 0.25 to 3.0%, of a resin which serves to add quick tack and strength to the adhesive. Examples -of resinous adhesives that may be used include solutions of polyvinyl chloride or polyvinyl acetate or copolymers thereof in organic solvents.

The adhesive applied to the fibers and the backing is dried to a non-tacky state, either naturally or artificially, without compacting the web. This prevents the adhesive coating on any fibers from adhering to any other fiber or to the backing, except at the points Where the fibers are in contact with each other and the backing, in the uncompressed, three-dimensional, random arrangement in which the web is initially formed. This arrangement forms innumerable intercommunicating voids in the web so that air can pass through the web, but only at a relatively low rate. The vast number of voids of air spaces in the web makes the structure eminently suitable for use as an air filter.

The filter, comprising the brous web 3 and the resin coated open cloth backing 2 to which it is adhered, may be cut into any desired shape. lIt is self-Sustaining and deformable, conforming readily to the contour of irregularly shaped objects to form a seal with the wall surfaces of said objects. In FIGS. l and 2 the filter is shown positioned in a rectangular duct 4 which constitutes part of an air-conditioning or heating system. The filter is slit inwardly from its outer edges, as indicated at 5, and its edges are then bent at right angles to form a rim 6. If the filter is to have square corners, the slits 5 preferably extend diagonally at the corners. A strip 7 of tape is adhered to the rim 6 to hold the corners of the rim in place and to impart strength to the filter.

The tape 7 may be adhered to the rim of the filter after the filter has been deformed to fit accurately in the duct in which it is to be used, or may be adhered first to form a substantially straight rim on all four edges of the filter, and the filter may then be deformed to fit the duct accurately. In either case the frictional engagement of the rim 6 with the inner surfaces of the walls of the duct 4 holds the lfilter in position in the duct and provides an eflicient seal to prevent the egress of air around the edges of the filter.

If desired, the tape may be applied partly to the rim of the filter and partly to the inner wall surfaces of the duct to provide an adhesive means for holding the filter against the wall surfaces. The tape also forms a seal around the edges of the filter.

Preferably the fibrous web 3 is on the outside of the foraminated backing 2, so that when the lter is positioned in the duct, the fibrous web is in frictional contact with the inner wall surfaces of the duct to form a seal between the rim of the filter and the wall surfaces of the duct. The deformability of the foraminated backing material makes it capable of frictionally holding the fibrous web against the Wall surfaces to provide an efficient seal around the edges of the filter regardless of the specific cross sectional shape of the opening in which it is positioned. The backing also provides mechanical reinforcement for the fibrous web.

The resin coated open cloth fabric may be adhered to both outer surfaces of the fibrous web to provide additional strength, if desired.

Although I have described a preferred embodiment of the invention in considerable detail, it will be understood that the description thereof is intended to be illustrative, rather than restrictive, as many details may be modified or changed without departing from the spirit or scope of the invention. Accordingly, I do not desire to be restricted to the exact construction described.

I claim:

1. A self-sustaining, deformable filter comprising an adhesively bonded three-dimensional randomly arranged porous fibrous web adhered to a foraminated, self-sustaining deformable resin coated open cloth, the edges of said filter being bent to form a rim extending perpendicularly to the body portion of said lter, and a tape secured to said rim.

2. A self-sustaining, deformable filter comprising an adhesively bonded three-dimensional randomly arranged porous fibrous web adhered to a foraminated, self-sustaining deformable resin coated open cloth, the edges of said filter being bent to form a rim extending perpendicularly to the body portion of said filter, the fibrous web being on the outer surface of said rim, and a tape adhered to the outer surface of the fibrous web portion of said rim, said tape being of less width than the height of said rim, whereby said fibrous web extends outwardly beyond at least one edge of said tape.

3. A self-sustaining, deformable lter comprising an adhesively bonded three-dimensional randomly arranged porous fibrous web adhered to a foraminated, self-sustaining deformable resin coated open cloth, the outer edges of said filter being slit and extending angularly to -form a rim extending perpendicularly to the body portion of said filter around each edge of said filter, and a tape adhesively secured to said rim.

4. A self-sustaining, deformable filter comprising a self-sustaining, deformable, resin coated open cloth and a porous fibrous web adhered thereto, said filter being shaped to ft an opening and deformed to provide an integral rim extending perpendicularly to the body portion of said lter, said rim being adapted to press said fibrous web into sealing engagement with the wall surfaces dening said opening, and a tape secured to said rim to hold it in place.

5. In combination with a walled surface defining an opening, an air filter comprising a self-sustaining, deformable, resin coated open cloth, a porous fibrous Web secured to said cloth, said cloth and web being bent to provide a rim extending perpendicularly to the body portion of said filter in frictional contact with said walled surface, and an adhesive tape securing said rim in place.

6. In combination with a walled surface defining an opening, an air filter comprising a self-sustaining, deformable, resin coated open cloth, a porous fibrous web secured to said cloth, said cloth and web having a plurality of slits extending inwardly from their outer edges to facilitate bending of the outer edge portions of said filter, the outer edge portions of said filter being -bent to provide a rim extending perpendicularly to the body portion of said filter in frictional contact with said walled surface, and an adhesive tape securing said rim in place.

7. In combination with a walled surface defining an opening, an air filter comprising a self-sustaining, deform. able, resin coated open cloth, a porous fibrous web secured to said cloth, said cloth and web being bent to provide a rim extending perpendicularly to the body portion of said lter with said web on the outer surface of said rim, the fibrous web on the outer surface of said rim being in sealing engagement with said walled surface, and an adhesive tape securing said rim in place.

8. A self-sustaining, deformable lter comprising a self-sustaining, deformable, resin coated open cloth, a porous fibrous web adhesively bonded to said cloth, said lter being deformed to provide a rim extending perpendicularly to the body portion of said lter, said rim being adpated to it an opening defined by a Walled surface, and a tape of less Width than the height of said rim wrapped around the outer surface of said rim, said tape leaving a portion of the brous web exposed around the entire perimeter of said rim, said exposed brous web portion forming a sealing engagement with the wall surface defining said opening.

References Cited in the le of this patent UNITED STATES PATENTS Bacon Aug. 30, Gaarder July 19, Sidebotham Dec. 6, Ensign et al June 19, Davis Apr. 25, Lang Sept. 12, Guyer I an. 2, Scholl Mar. 31, Fleming May 18, Klein Oct. 30, Maisel Mar. 5, 

